Transmission by electric oscillations



' May". I.

n Ai' A {it} 1,627,767 L.'N.BRILLOUIN ETAL'y y'rmmsmssnm BY' BLETaIc oscILLA'rIoNs fmed Aug. 1 0. 1925 V1o sheets-snmA 2 10 1927. v 1 627 767 May 1 n l.. N. BRILLoulN ET AL 7 TRANSMISSION BY ELECTRIC OSCILLATIONS K F11e 1Au.10. 1925 1o shuts-sheet 3 f rz-73.22 n 'F923 May 10. 1927.

` 1,627,165 kL. N. BRILLOUIN ETKL TRNSIIVKSSION BY ELECTRIC OSCILLTIONS 10 Sheets-Sheet 4,

\ Find-Aug. 1o. 1925 May 1 0. 1927;l

n v 1,627,767 L. n gaiLLoulN l-:1'` AL f @Ransussxon BY ELECTRIC oscI'LLA'rIoNs 'A Filed Aug. 1o. 19,25 10 shuts-sn. 5

rija;

May 1o, 1927.

` y1,627,767 |..`N. BRILLoUlN ET AL y TRNSIISSION BY ELECTRIC OSCILMTIONS Filed Aug. l0, 1925 10 Shggfg-Shggt 7 May 1o, 1927. I

' l1,627,767 L. N. BRILLOUIN ET AL TRANSMISSION BY ELECTRIC osclLLATIoNs Filed' Az. 1o. 1925 Y 1o sheds-'sneu 3,.

v ,Kauf Y Patented May 10, 1927.

UNITED", STATES 1,627,767' PATENT o-ififirzfa.`v

LoN NICOLAS BRI'LLoUIN ANDEMILE `MARIErmiNoIs ERoMY,'oE1 AnfIs, FRANCE.

TRANSMISSION BY ELECTRIC osoILLATIoNs.

AApplication nica .ingu-st io, 19215, serial No. 49,394, and in France November 1o, 1924.' i

Uur invention relates .to compound circuits oscillating on a plurality o f wavelengths` which can be` predetermined by choosing suitably the electric c,hanacteristicsyy of the parts composing the circuits. yThese can be used witi` advantage as described hereinafter for transmission by electric .oscillations, telephonie or telegraphic, with or` without wire. A l p y y Our invention has chiefly for object` the meansfor connecting such circuits in transmission stations with the antenna, one.0r`

inore wave lengths being used simultaneously for the transmission. We y .more partici'ilarly a transmission borne simultaneously by two waves in the same or opposite directions, devices for protecting the transmission against strays *whetherv thesev be `intentional or accidentalv and ar-V rangements for secret communication.

`The appended drawings will help the inf vention to be better understood. y, n

lFig. v`1 is a diagram of acompound circuit i ofthe most general type.

Figsf.) to'21 are diagrams of several compound oscillatingcircuits4 deriving from the one shown on Fig. 1. K' l' Figs. 22 `to 28 show'seif'eral `ways of coupling such circuits with an antenna.

Figs. 29 to 33` relate to radio communication stations usingcompound circuits os cil-latinlg on several wave-len K hs. v

Figs 34, k35 and Sdshow t e connections used in stations emitting two waves alternately.

Figs. 37, 38 andV 39 show `the connections used in4 stations receiving. the two waves,

Figs. wand 41 show the connections used forfpreventing the reception being confused byanother station.

Figures 42 to 48 relate to arrangements denser is'taken out of the compound-circuit for secret communication.

vFigure 1 `shows the most general of 4compound circuits oscillating onseveral wavelengths. It comprises three secondary circuits which we shall henceforward term plug circuits.. By suppressing certain elef ments ofl these circuits simpler vcompoundv circuitsfcan be. obtained oscillating only on two Wa\-'e-lengths yThese simpler circuits can be grouped in three classes according to the number of plug circuits used. y p

Classi. Circuits comprising a coil and a condenser in series with` a compound, semi-compound or describe.

simple plug circuit.l

(Figs. 2 to 5)' and which can V.be.obtained` by suppressing .from the general circuit of Fig. 1 L1C1 and the plug circuit L C,l and by simplifying according to the case, the plug circuit C2 C:i L2 L3.

or simple plug circuits (Figs. 6 to: .111). lThese circuits can be obtained suppressing `from the generalfcircuit L4, C4 and by simplifying one after 4the otherthe two vplug circuits L CL1 C1r and vL2 C2 L., C3.`

Class 3. Circuits comprising three simple plugcircuits (Fi-g. 12) which a-reobtained by suppressing from the general circuit L1 C1, L2 and C3.

The diagrams drawn are not the only possible ones. It isV suilicient to replace one ormore of the secondary ,plug circuits bylequivalent circuits oscillating on one wave Class 2. Circuits comprising ka coilor a condenser in series with two semi-.compound y Way of example the three plug circuitsiof F ig. 17 which are equivalent to- `the-compound plugcircuitof Fig. 14 and the plugcircuits of Figs. 18 and 19 which are'respectively equivalent to the semi-Conil pound plug circuits of Figs. 15 and 16 are?.

shown. f f

It is easy to see that comparatively tricate circuits such` as `those of Figs. 17` to l19 are equivalent to less intricate ones, suchv as those shown on Figs. 13 to 16. `'For in-' vstance the compound plug circuit of Fig. 14

canbediagrammatized as on Fig.` 20'which.l

makes it appear as a` simple plug circuit connected through the cent-ers of `the vcoil and of the condenser. Evidently without changing its' properties it can be provided with either a shunted coil or a shuiited con-f v.denser (,Fig. 17) or with both (Fig. 21).

`In asimilarlina-nner iffa coil or a condiagrams If the plug circuit-s (Figs. 13 to 21) are inserted in lieu of the equivalent plug cirycuits of the eleven circuits shown on Figs. -2 to 12 agreat number of` new compound circuits would bey obtained diagrams of which could be. drawnA easily.

To makeup antennvibrating withl `two wave-'lengths by using. these compound circuits it is only necessary yto replace vby a derivation connecting an antenna lto earth,

either a capacity in case a short antenna is used, which acts very much like a capacity (this antenna could be also connected in parallel with the capacity) or a coil connected in series with a capacity in case a long antenna is used wave length ot which is near that of one of the waves used.

Thus a great number of antennae having two wave lengths can be made up diagrams of which can be easily drawn by using the eleven diagrams of compound circuits (Figs. 2 to 12). By way of example Figures 22 to 28 show some forms of execution of such two-waver antennae.

Figures 22, 23, 24: and 25 show two-wave antenna circuits produced with short antennae connected with the circuits of Figures 2, 6, 9 and 11. v v

Figures 26, 27 and 28 show two wave antenna circuits produced with longv antennae connected with the circuits ot Figures 2, 6 and 7. The parts of these antenna circuits are shown as stationary on the abovementioned ligures but of course -they can be made adjustable so as to allow the adjustment of the antenna on two given wave lengths. l

For coupling these circuits the following directions should be heeded.

Vith the circuits ot class 1 (Figs. 2 to 5) used in practice fortwo waveshaving a great difference between their wave-lengths the two waves oscillate separately oneL in the'plug circuit and the other in the derivation and generally the shorter one oscillates in the former and the longer in the The current and the voltage in the plugv `the contrary in the derivation, the current and the voltage at the terminals ot the condenser will be small for-the shorter and great for the longer wave. y

The voltage between the terminals of the coil will be great for the currents corresponding to both waves. The direction ot the current in the coils of the plug circuit and of the derivation is the same vor not according to the wave to which said current corresponds. Y y

In the circuit of class 2 (Figs. 6 to 11) and of class 3 (Fig. 12) which can be used for waves ot near wave-lengths the separation between the waves is not as absolute. However if the two plug circuits (Class 2) or two ot the plug circuits (class 8) are tuned to the same frequency one ot' the waves oscillates in these two plug circuits, no current passing through the connecting coil, condenser or plug circuit and no voltage dilterence existingbetween the terminals of said connecting device. The currents in the coils of the` two plug circuit have relative directions which diler according to the wave which makes them oscillate.

Consequently for coupling the circuits of class 2 and class 3 the connections can be made at the terminals of the principal plug circuits if both waves are to be emitted or received, or else'at the terminals of the connecting coil, condenser or plug circuit, it' the wave oscillating in the plug circuits is to be eliminated so as to allow the reception or emission of the other.

Magnetic couplings can also be used either through a coil coupled inductively with the connecting coil or condenser when the wave oscillating in the plug circuits is to be eliminated or else through two coils inserted in series and coupled inductively with the coils of the two plug circuit-s. It these couplings the diagram of Fig. 5 and are adapted forv emittingk two wave-lengths comparatively dillerent one from the other (the ratio of the wave-lengths rnot being less than 2). The others using the diagram of Fig. 11

are adapted for emitting comparatively near wave-lengths.

(A) Simultaneous emissio/lts.

Fig. 29 shows in a general and diagrammatical manner an emitting station antenna f otwhich vibrates through induction.

Two autodyne circuits ied by the vacuum tubes 8 and 9 and each adjusted for one ol the wave-lengths emitted are connected with vthe grids ot the two coupling tubes 10 and 11; latter comprise in their plate circuit coils each coupled with the corresponding coil 1 or 3 of the antenna circuit similar to that shown on Fig. 23. When not widely different wave-lengths are used the coils of the plate circuits would be coupled with the coils of plugcircuits connected with the antenna.

Figures 30, 31, 32 and 38 show severalvk connections where only two vacuum tubes are needed. The connections as on Figure 3() cannot be vused with an antenna as it would oblige a grid to be connected with earth; on the contrary Figures 31 and 32 show connections which may beused with an antenna as does also Figure 38 which is specially adapted for use with wavelengths not widely different.

The connections of Fig. 30 afford a verv good selection between the two waves where'- as those ot' Figures 31, 32 and 33, it no special care is taken altord only an approximate selection, the two waves influencing eachother.l` y t I, p f

This interference ,can be avoided if the changent the direction of the current inv thetwo coilsof the antenna according to the f wave emitted ismadejuse of. It is sufficient to'couple the antenna coils with two plate coils mounted in series in such a manner as to make; the currentsgproduced by one Wave flow in the same direction, whereas. thosej produced bythe other will `How yin opposite directions and annul each other.

By these means each valve can bev protected from the' wave which ,it does i not produce andy is not influenced thereby.` f Alternatejfemz'saions.

These' `,can be made` with two audions (or groupsof audions) which areset oscillating one after fthe other, either by feeding the` plates with alternating potentials phases of which are in opposition, as shown on Fig. 34,y The primary 13 of a `transformer is fed with A. C. and itssecondary is inserted between'the two plates ofwhicheach works only4 during the half period of the feeding current when it is positive with reference to the corresponding filament.

, It isfeasy to understand without any further explanation nor drawing that a similar device `can be provided for by a ticker which, will set the tubes working alternately by o ening and closing alternately the circuits a lewin the said tubes to work.

Fig. 5 shows how the two'alternatingI waves can bevproduced by. only one audion @Glidingl (ory set of au'dions in parallel) with a ticker connecting the grid with eitherthe coil 14 orthe coil 15, These coils are made up `in a Vmanner such as will givethe waves produced in theK *antenna circuit the chosen wave-lengths accor-din to the coil (14, or 15)` which `is inserted; in the circuit. It shouldbe noted that for a same direction of flowof'the current in thecoil 15 the current flows through coil 5 inonevdirection or the other according as toV whether the longer or the :shorter of thetwofwave-lengths is used The coils 14 andl shouldftherefore i be,- wound' in opposite ".directions` soV thaty either oney or the other' lwave can pass ac-` to kthe position of thefticker, Y Allt e devices described'hereinbefore and' working withfeith-er "a transformer or a vticker canbe used with modulated waves en iitt'edV simultaneously oralternatively aty any frequency, the frequencies being 'equal' or not.,A i 'owev'er' in vthe case of powerful stations lthe connections Ashown on Figures -30v to 33"'havethe following drawbacks. 1, The switching open of circuits wherev through-flow comparatively strong currents;` 2"?. The cutting of connections at points under y voltage which Q necessitates special care f forfthe'insulation ofthe ticker and of .its

feeding batteries. avoided by usingthe connections shown on Figure 36 which can serve `for many larrangements. I n -f v On Figure 36 given by way the compound circuit yshown adapted for comparatively different wave lengths; alarge condenser 17 `is inserted at the foot of the antenna to separate it from the ground; The antenna circuit is, connected with the grids of the two tubes by means of the coils 2O and 21 coupled respectively with the coils 1 and 3, latter coi-1s being inserted in the plate circuits. Two switches 18 and 19 arel provided rbetweenl the grids and the filaments of the tubes.

If these switches are operated alternately so `that one is open when the other is shut andy shut 4when the other is `-open the two of example,

wavesr willbe emitted alternately. For this purpose it is sutlicient to replace the: two

grids', the body ofthe ticker being grounded.

The drawbacks pointed out hereinabove are avoided as it is the grid circuits which are opened and closed and through these grid circuits only very small currents pass. The ticker being grounded the points where the circuits are cut are at lno high voltage.A

These connections allow different arrangements to be provided for instance.

(a.) By closingthe two switches,y twoundamped waves will be emitted simultaneously; y,

(b.) `By ,closing `one the other,` D' emitted.`

(c.) By these by a be modulated to the rythm of therfticker, thereby allowing: y y

Theemission of one modulated wave;

switch andA opening only one undamped wave is replacingthe switches or one of the beats of rIhese drawbacks can be` is the one ticker the corresponding wave can i ssiV The emissionof two `waves modulated at i different frequencies; p i f The emission of amodulated waved and of an undampedA one. l i

By using one ticker opening and closing simultaneously or alternately the two4 `two waves may be emitted together'v circuits,

orin alternation which aremodu'lated at thel same frequency.

On Fig. 36 shown threeamm-eters 22,y

22 gives the cur- 22 and 22. he ammeter i rent producedrin theantenna by the ysum of the two Waves whereas. the ammeters 22 and 22 give the current corregponding to each separate wave.' i

The corresponding receiving station `is provided with an antenna of oner of the yabove describedy types.

The Figures 37, 38

and 39 show byY way of example connections which may be used.

- (a.) The connections shown on Figures 37 l and 38 l'irstof which `relatesto'waves of the second to waves of not widely differenty wave-lengths, comprise two circuits; each of these is an oscillating suitably tuned circuit comprising a coil 23 and-a condenser 24 and is coupledpwith the coils l and 3 (Fig. 37 or with the coils 5 (Fig. 38)` ot the antenna circuit through its coils 25, 26 or 27, 28. vThe oscillating circuit is coupled or connected on the other hand with an amplifier (not shown); as stated hereinabove the current iows through the coils '1 and 3 or through the twoV coils 5 in the same or in opposite directions according as to whether it is produced by the shortest or the longest wave.

Therefore the coils 25 and 26 for instance should be wound in the same direction and the coils 27 and 28 in opposite directions. In one of the oscillating lcircuits comprising one of these groups of coils the curi-ents produced by one of the waves'will be `added and those produced by the other will be in opposition; thus by suitable adjustments the etfects ot" one of the waves can be annihilated in each circuit, and two absolutely independelit receivers will be provided tor.

(b.) In the diagram shown on Figure 39 the secondary comprises a two-wave circuit of one of the abovedescribed types which acts upon amplifiers (not shown). iVith such a diagram the corresponding coils must be coupled together; the coupling may be besides be replaced by a direct connection.

The preceding descriptions of receiving or emitting stations are suiiicient, without any longer explanations and without any further diagrams, to make clear the execution of radio-telephonie stations emitting on one wavelength and receiving on another whereby a conversation is possible like on an ordinary wire circuit. j

Three forms of execution oty a device for protection against strays whether intentionally emitted by another station or not are described hereinbelow.

(A.) The transmission is operated on two simultaneous waves of greatly dii'erent trequencies. The reception is such as will comprise tworeceiversveach of which is influenced by only one oit' the two waves, the other wave having no effect upon the receiver considered. Thus it one ot the waves is confused it will always be possible to receive on the other.

(B.) The transmission is operated on one wave only whereby the stray wave can be eliminated even if it has a very near wavelength.

In this case compound circuits ot the groups 2 and 3 should be used. s

By way of example Fig. 40 shows a receiver of this type. The antenna is small and can vibrate for two wave-lengths not widely different. The antenna circuit is of the type shown on Fig. 12. This circuit comprises three plug circuits 92-93 and 94. One of these, 92 is inserted in the antenna; A switch 95 allows the plug circuits 93 and 94 to be cut 0H the main circuit whereby an ordinary antenna is left so as to make the adjustment easier. If the two circuits 92 and 93 are adjusted exactly for the same frequency, one of the vwaves passing through the antenna can oscillate through these circuits. The vibrations ot the antenna produced by this wave will only act upon these plug circuits 92 and 93. The plug circuit 94 is independent of said wave and only vibrates through the other.

This second wavey is the longer or the shorter one according as to whether the oscillating period of the circuit 94 is greater or smaller than theone of the wave which can oscillate in the adjusted circuits 92 and 93.

A secondary circuit 96 is coupled induc-v tively with the antenna by means of two small coils 97 and 98 as explained hereinabove.

The circuit is adjusted as follows for working:

(lo.) The plug-circuits 92 and 93' are lirst adjusted ."or the wave-length of the wave to be received. This can be done methodically by using 'the switch 95. Latter is first open andthe antenna is adjusted in the usual manner for the wave to be received. The switch 95 is then closed and the plug circuit 93 is adjusted without touching any more 92; f

(20.) The antenna is then adjusted with the stray wave by adjust-ing the circuit 94, without touching 92 nor 93, the two adjustments having no inliuence one on the other.

It is preferable that the plug circuit 94 should be similar to thek two others so that by making its capacity vary above and below its mean value, the secondpwave-'length with which the antenna is timed is longer or shorter than the working wave-length,

whereby `the stray wave can be eliminated by the plug circuit 94 in all cases;

3Q.) The secondary circuit 96 is adjusted vfor the working wave and the couplings of the coils 97 and 98 are disposed so as to annul completely the currents induced' by the stray wave (this is provided for by making use of the change in the direction of flow of the currents in the circuits 92 and 93 according as to whether the antenna vibrates with one or the other wave). Thus the two waves can be completely separated, even if their wave-lengths are very near. Howevery if the strays are very powerful and it is difiicult to find a complete extinction thereof, they can be choked without choking the useful wave. In view of this it is sufficient to provide the plug l94 with a shunted resistance 90 or with any other damping arrangement. This damping has no effect on immer y the working wave as no current-produced by n groupsof coils'27w28 and 25-26 is-insert'edr` .in the gridcircuit sind `wave y passes anymore. through `the plug ycircuit .94. On the centrar this damping chokes the stray wave entirely. This arrangement 4protects very simply and very 'efiiclentlsy against strays, and is also `easier to set up than the usualconnections.

The advantages are the following:

(51.) The two adjustments ldo not interfere at all and a stra-y wave canbe completelyeliminated 4whatever its wavelength 1s without the tuning to kthe .working wave needed tol be correct-ed.

:(20.1) The separation ofy the two waves and the elimination of the stray Ywave c-an be com lete; I

The antenna circuit canibe damped .for the stray wave .without lthe working wave being choked. f

The preceding method allows an easy fand simple'protection. against one stray `wave to whichone'of the circuits, is tuned; the third `method described hereinbelow does away with this .'tuning. It consists in transmittin iby two waves of Averyenear `frequencies, ftlie emissions on Athe two waves being `alternated at `a frequency F @which `can be suprasonorous in tthe case `of radiotelelzih-y ony). The receiver comprises two ydetecting .ftubes each lactuated by one. of the :waves and insert-ed soy asfto.A send current in opposite directions towards one same receiver or amplitier. If a stray `wave is emitted. ata Fire- .quencyfnear that o-onefoflthe wavesit will make 4the antenna :vibrate on both its waves separately and ,as the :tubes .are inserted in opposition vone to eachother the action of the stray wave onathe receiverwill be the difference 'between its action on both lamps. The receiver will bethus veryslightlyziniiuenced. V'()n :the .contrary the alternating .waves emitted .by the emitting station actk one after fthe other but .withfull efficiency .onithe receiver `which will bevery strongly ipfluenced.

Fig. 4=showsany arrangement of this type. l

The:oscillatingicircuits 29 and 30 of the antennaareicoup'led with :the coils' 25 and 26 on one hand and 27 and 28 on the other aslexplaiued hereinabove. Each .of `these offoneof the detecting ftubes SandlBQ. Theeplate circuits comprising or not coils such vas33 4and 34; l'for regenerational-e connected with the prim-ary windings 35, `36 otra transformer. These windings are wound in opposite directions .andprovided with shunted .c ondensers 37 and38 `through which high-.frequency currents. can pass rthe secondary 39 `of thetransformer is connected with kthe yamplifier 40 and :can be :provided-with .an adjustable shunt-ed condenser.

vThe workingfoffthe device is easy-to understand. iIt-a stray wave isenutted, its

through the coils and 36 of .the transformer will be opposed andthe current .in-

duced in the secondary `.will depend solely on the .difference of .the currents produced `in the two tubes by the `stray wave.

In the caseiofw-the working waves,.onthe contrary which-alternate at-the frequency F, the first wave is received by the circuit of the tubeBl-and by .reason of the tunin will have no effect on the tube Theitu' 31 detects this wave and the current yflowing through the winding y35 will varyand consequently induce in the winding 39 and fthe amplifier 40 acurrent having acertain` direetion. When the second wavelsucceeds toithe first one the same phenomena begin Vover again but through the tube 32.a*nd'the=wind ing 36. The coils 35 and 36 being wound .in opposite directions, the current induced in the `secondary 39 will have afdirectionop-posite to that Offthe current previously induced, consequently an alternating currentof frequency F will flow through the coil :39 and wave types described hereinabove, whether these produce widelydifferent wave lengths or not. The waves are modulated at a musicalor at an ultrasonorous frequency .which is the same forboth waves. l

The two emissicnsfcan'besimultaneous or alternating .by means of a Akey which can changethe phase ofthe modulation for-one ofthe waves sothat according tothe position ol the said l cy,4modulations of thetwo waves will be instep or ilropposition.

`lheconnections should lbe-lsuch for yinstance as to cause the modulations tolbe in step (simultaneous emissions) Awhen theikey iszraised'and in opposition (alternating emissions) when it is lowered.

. The receiver comprises:

(lo.)` A doublewave receiving circuit Aadjusted on the two wave lengthsused v-or the transmission `(2".) `Selecting circuits adjusted for one wave-lengthonly;

(3.) Two detecting valves detecting'each` y on the receiving device connected with them be completely nil or partially diminished when the two waves pass at the same time.

Thus nothing or little is heard when the key is raised as thenthe two waves pass both together to the receiving device. On t-hev contrary when the key is lowered, the waves alternate and both actuate the receiving device.

Nothing will. be heard therefore unless the key is lowered when the emitting station will be heard. y

But a spying station using a receiver; ad.- ustable to only one wave-length and adjusted to receive one of the two waves emitted will receive without any interruption whether the key be raised or lowered. The working of said key only produces a change in the phase of the .modulation of the wave receiver and cannot be detected. The spy has therefore the ii'npression of a continuous emission.

rlhe modulation can be of any suitable frequency which can be a musical. one (1000 periods per second for instance) on which case no further detection is required for hearing. The frequency could also be suprasonorous in which case it is necessary to modulate the modulations of the wave either when emitting or when receiving. These second modulations are detected again so as to allow hearing.

The emission can be made by any of the abovedescribed emitting devices.V The changing of phase can be made by one of the following methods.

(A.) The primary modulation being produced by a ticker or by a rotating switch the changing of phase is operated by changing through the key the connection of the contacts connected to the grid circuits.

Figure i2 shows an emittingstation of this type.

The oscillating double-wave circuit comprises a. coil l, a capacity 2 and a plug circuit constituted by the coil l is grounded and the other is connected to the antenna. The plates of the two vacuum tubes producing the waves are connected each to one of the terminals of the capacity 2. The grids of the two lamps are each connected with a winding coupled with one of the coils l or 3. One of these windings is connected with the Contact part 5l of a ticker 52 connected with the filaments of the tubes. The second winding is connected with a key which connects it either when the device is not working with a terminal 54 connected with the other winding or else when it is working with a Aterminal 55 connected with the other contact part 5G of theticker 52. Latter is shown diagrammatieally as a blade y suitably kept vibrating by means not shown yon the drawing. yThis blade 52 comes alternately 1n contact with the Contact parts 5l yand 5G. Of course this blade can be replaced by any other suitable device such as a rotating switch for instance.y lVhen the key is at its rest position against the terminal 54, both waves are emitted simultaneously each time the ticker 52 comes into contact with either contact part 5l or 56.

(B.) If themodulation is .operatedby feeding the plates with A. C., the changing of phase can be made by reversing through a suitable switch the direction of the winding of a. coil of one of the feeding transformers. To help this switching the opening of the circuitis preferably made in oil or an intermediary circuit of low voltage.

Figure 45 shows an emitting device of this type wherein a vlow tension intermediary circuit is opened and shut for operating.

. The double wave oscillating circuit is similar 'lhe grids of the wave' to that of Fig. eil. generating tubes are' each connected to one end of one of the coils l or 3. The A. C. supply 57 feeds iu series or in. parallel on. one hand the primary 5S of a transformer 53--59, on the other hand the primary li() of another transformer 60, 6l. The secondary winding 6l of latter transformer 'is connected to a hand lever yhaving twok contact parts (i3-64 (a rest and a working contact part) connected with the two ends of the primary of another transformer k65--66- The other end` of the secondary 61 is connected with the middle of said primary 65. The two windings 59, 66 provided with shunted condensers are inserted between the plates of the two lamps. According as the coil 65 is fed through the contact 63 or the contact G4 the two waves produced in the antennaby the windings 59 and G6 will be in step or in opposition.

The receiver corresponding to either above described emitters is of the type shown Fig. 4:1; the antenna can be of the type receiving two wave lengths very far apart as well as of the type receiving two wave lengths very near each other as shown on Fig. 41.

In the case of wireless secret telephony, the emission can be cut up and sent alternately on one of the working waves.v A two-wave receiver is used which records the twowaves with the same intensity so as to reconstitute the emission. on the contrary will only hear on either wave unintelligible or cutup words.

c The emitting station is of any of the above described types emitting alternately two waves.

The waves are cuteither by feeding the plates with A. C. in phase opposition for the two'waves or else by means of a ticker l or of a rotating switch. l

The telephonie modulation is produced by any of the known methods.

If the emitting station uses as in Fig; 35

only one tube the modulating device is any A spying station Cil yio

of the usual devices usedfor that purpose. Fig. liet, sho wsy 'an emittinr stationh ofV this type. The. `rot.'iv1,1.i.1.1.f,f.Switali,7.0. connects dIternately. the gridofthe vacuum tube 71j with oneJ of'tlie t-u'o coils l; ll'inserted in the circuit opposite directions., These coils` coupled with vthe coil 5A of a compound .circuit Comprising tw@ plus. creui'ts 5-16 compel alternately, the antenna to Vpircducc' the correspondin'gfwave., The voltage of; the gridof theftuhe 71jis modhlatedfhy the vacuum tube 7 3 filament and late' of which are 'connected' through the con ensei* 74`ofthe-tulle 7 f1. Its gridpotential is modulatedhy. the circuit: 7 5 whereinis inserted the microphone 7 t'of the tele. hpnl@ apparatus.. '1T e, Connectionsas drawn Oiilla Mellow the drawbackofpmdcina by the modulation ofthe grid: circuit through the tube- 7 3' some. distortien' of. the. words spoken and Somazunsteadiness. Off th. 'Working THiS-is; avodedby. using, the F'gig'.;` 45. The n iodnla,ting` tube 73' grid potential Gti which ijsmodillatedj by the micw'phone tthroughthe transfrim'er 715 acts on the voltage ofgthepljateof the Wayg.

generating. Connectln's r. the;

tube is fedin parallelby: the same supply as the Lp1ite..Ottlie. emitting', tube. 1.1.1; the commoncrcuit is; insel:ted,k alfcoilj 915 havin .a

n the'osillating tubes Self-82'.A es

great. impedance. ffr thfese telephaniq, re-

uencies and. ada .tedl to. keepV the` culfl'ent d. by the: sur Y lSub,Shuut-.ially wnstant.

Thus:lv the mod-u tns. Qf the plate Current in the. en.,iittililgr tube areiequal, ,f and'. opposed to.' those`- Qf, theliplate- Current :in the "modu-` lating tube. whereby the. waives. transmitted are slitablrmodillated. c

` The c.oi1,`9l is provided with` a, small shunted capacity 9Qthroughwhieh theA high frequency Currents cart pass. withut; .the impe/dante of. the., Circuit beingE diminished for, currents at` telephonie :freqllelieies.v

' Zhen the emitting station'comprises4k two tubes, (0r Setsofltibejslihe modulating. de-

vice should be such as willmodulatefthe two sets of tubest,he connections, providing for the identity` of the modulations inI eachl of them? t. Y. K Fig. 4.6 shows a stationof this. type connections of which are. similar to thoseoff Fi g. 36.,- The rotating siivitcliB()` is disposed between the two., gridy circuits. of. the tubes 81.-.82 onK one hand and, thel condenser 83. onthe other., The terminals 0f. Said COIL- denser are connectedftothe; filament andl the plate ofI vacuum.' tubey 84', grid of which is modulated;throughthe transformer 85 primary of which comprises the` microphone 186. The. vacuum tube 84 meduletesl alternately the. urrnts passing. in thel grid circuits; of

The tworwaye compound circuit" 1,.-,3 connected.` with the antenna vibrates alternately'with one or the,V

a this type.

.plate'off the modulatingfseparately and simultaneously by thextubes other wavefwith'out thischang-ing affecting the modulation which is. borne! inthe same` manner b'y either wave emitted.

When the platesare fed with A. C. in view of cuttinglthe emitting waves periodi? cally, abuzzing is heard in the receiver which is caused'by the sinusoidal.modulation produced by the A. C. This buzzing isfnot lated by the microphone circuit?, thealterna- .Connections 0f,y

tions following an rythm desired: audit-he words are carried alternately by either wave'.

The required secret transmission isithus established withoutany cutting of'the wares Fig, 47 showssuch an emitting station. of The: two waves are produced 8l.' and 82twhich make the double wave antenna. vibrate as explainedgwith reference to Fig. .36.- l f The gridcircuits ofbothtubes comprises a telephonie modulating device constituted by` a capacity 83 and 83 proVidedwith a shuntedvacuumtube workingrin a manner `similar tothat of tube Mot-Fig. 46;.. The

grids otthese modulatingvacuum tubes' are fed `with telephonie currents .through the transformers 85 and`85"; The primary coils of these transformers are connectedin parallel with the terminals ofthe secondary of ateleph'onic transformer 85A and alternately insertediin its circuit byv means ottlie rotatingvswitch 80. The. primary ofthe transformer 85`comp1ises a supply of'D. C. und the microphone 86.' c i The station works ner:

The two, waves. are emittedsimultaneously andfcontinually;:each of them is modulated by the microphonic'currents when the corresponding:transformer 85,01' S5"is inserted in the circuit through `the rotating;r switch 80 and non-modulated when such is not the case. If the switch 80 is built in such manner that. there is always one and one only: transformer insertedzin circuit at the same time, there is only one modulatedwaye, the other being then non-modulated antljtlie module tion passing fromf onel wayeto the other at the rythm givenb'y the switch.v n

VA' spy adjusted on one of vthe waves would hear, only duringI the periods when the, said wave is modulated so( that he would' only in the following man? receive fragmentary and unintelligible sounds as explained hereinabove with reference to the preceding diagrams of connections.

On the contrary a receiver which is adjusted for receiving both waves with the same intensity allows an interrupted hearing of the sounds which are thus built up again.

This arrangement shows the great adfantage for practical purposes that there is no opening of circuits under high potential or fed by strong D. C.

The only opening of va circuit is that made on the connecting circuit between the transformer 85 and the transformers S5 and S5 wherethrough only a weak A.. C. Hows.

It also solves the problem in the best manner possible inasmuch as it eliminates the periods 'of increase and decrease of each wave whereby the reception is purer.

.The corresponding receiver comprises:

(1.) A two-wave. collector y (2.) Two selecting circuits each of which is adjusted to receive oneof the waves;

(3.) Two detecting lamps acting in parallel on a telephonie amplifier.

This receiver can be of the type shown on lFig. 41 and adapted for receiving a modulation of telephonie frequency. The only difference would be that one of the windings or 36 in the coupling 35, 36, 39 should be reversed so a's to make thetwo detecting tubes work in parallel and not in opposition. Y

The couplings between the two selecting circuits through the coils 25, 26, 27 and 28 with the antenna should be adjustable so as to afford means for making equal the intensity of the received currents produced through both waves whereby undulating sounds are prevented; according to the case required the antenna. will be of the type receiving waves having wave-lengths greatly differing or not. Only one detecting tube may be used if the grid circuit of `said tube is connected with a part of the antenna circuit or of a secondary two-wave circuit beu tween the extremities of which the voltage' of the current produced by both waves is great (such as thev plugcircuit 29 for instancefof the antenna circuitv of Fig, Other antenna circuits can be used with their two secondary plug circuits inserted in series in the grid circuit of the detecting lamp. The diagrams can be easily drawn without any further details being given.

('ompoimd circuits used for elcctrc 00mmamcatzoas by were.

All the connections described hereinabove for radio-communication can be used. for high frequency telegraphic or telephonie transmissions by wire. More particularly the double-wavecircuits solve very well the problem of` a bilateral communication by wire with currents of two different frequencies.

The method of coupling a double-wave antenna with secondary circuits as described hereinbefore can be applied to the coupling of" any double-wave circuit with any secondary circuit and affords the means for separating completely two currents of different frequencies. These double-wave devices replace with advantage the known selecting devices used for the same purpose as it is easier to set up the corresponding connections and it selects the desired frequency without weakening it.

Lastly the two-wave circuits allow secret communications to be transmitted by wire as well as by radio either by telegraph or telephone. Similarly the communications can be protected against accidental or purposely made confusion.

By suitably combining these two forms of execution (unconfusable reception and'unde- `cipherable emission) a perfectly secret transmission-can be provided for; that is a spy ing station cannot decipher it if ithas not the other hand it is,

got the key and on impossible to confuse it. y

The coupling of such double-wave devices with the line wire is effected as in the case of ordinary circuits.y

Thecoupling can be an inductive electrostatic o`ne if a simple connection is used and the antenna is replaced by a condenser transmitting the oscillations from the circuits (as in the case of radio-communication the condenser must be connected with the circuit ata point where'the voltage corresponding to both waves is high). y The coupling can also be an inductive electromagnetic Aone if a double line wire vis used; in this case a coil is inserted in the circuit at apoint where the voltage corresponding to both waves is high. rI he coil could also be inserted in the plate circuit of a krelay vacuumtube grid of which is inserted in a two-wave circuitin a manner similar to that of the condenser described with reference'to the first wayv of coupling.k j

Lastly two coils could be inserted in the line wire, each of these being coupled with the coils of the compound circuit wherein the ktwo waves vibrate. f

What we claim is: 1. In arrangement for radiocommunication a compound circut'comprising a number of distinct plug circuits tuned to different wavelengths whereby the waves pass through the compound circuit in a given direction according to which plug circuit is tuned to them, and secondary circuits coupled with the plug circuits and tuned each to one of the said plug circuits, the direction of the windings in the couplings being determined so as to provide the addition of the effects produced by one of thev waves and the substantial cancellation of the effects produced by the others, the aerial being moreover connected with the compound circuit at those points where the potentials due to the different waves are the most different.

2.`An arrangement for radiocommunication comprising a transmitting set consist-- ing in a compound circuit as described in kclaim l and provided with emitting means,

each secondary circuit being provided with independent means for modulation and a receiving set consisting in a compound circuit as described in claim 1 and provided with receiving means, the corresponding plug circuitsin both emitting and transmitting circuits being tuned to the same wavelength.

3. An arrangement for radiocommunica- -secondary circuits to the same or to different receiving devices, the corresponding plug circuits in both emitting and transmitting circuits being tuned to the same wavelength.

4. An arrangement for radiocommunication comprising a transmitting set consisting in a compound circuit as claimed in claim l with two secondary circuits, two wavegenerating vacuum tubes, the grids of which are inserted each in the corresponding secondary circuit, keys inserted in each of said secondary circuits, means for manipulating automatically both keys when desired and a switching device adapted to close alternatingly at statedl intervals both secondary circuits and a receiving .set consisting in a compoundcircuit as claimed in claim l with two secondary circuits, two receiving units and a switch adapted to connect at will the secondary circuit either to the same or to different receiving units, the corresponding plug circuits in both emitting and transmitting circuits being tuned to the saine wavelength. y

In testimony whereof we have signed our names to this specification. 

